They sell those giftcards by the way, so that doesn't guarantee they'd not use it in someone to get drugs or whatever.
Furthermore, I think it is kind of a moot point here. There is no right or wrong. A safety issue for sure. But no one is less Christian, holy or good than the other. That seems to be what this steam has evolved into...an argument of who is more christian or "right," the person who gives money without judgement or the person who doesn't.
It is all in your head and heart right now, really. If you feel good because you feel you helped someone...great. If you feel you did the right thing because you didn't give the guy money for fear of funding a habit or whatever...great.
In the big picture, from a Christian perspective, only God knows what everyone's motives are when they are choosing to help a "homeless" person asks for money. This includes what's in the heart of the "homeless man." For all we know, depending on his motives for begging, if he is a scammer or addict using people, ironically, the beggar is probably the person who is at most risk of being in the wrong.
As for the rest of us, because we choose to help someone, doesn't mean we're doing a good thing, or that we're necessecarily doing it for the well-being of someone. If we feel we did the right thing because you got a good feeling from it, who is benefitting? The beggar or you? The beggar is groveling to feed his stomach or habit. How miserable. You are feeling good because you eased your concience that you were in a fortunate position (only by the grace of God) to temporarily help this person. If you truly believed you did the right thing, would you need to ask us here? Seems like you're looking for justification. Or maybe a pat on the back because you posted your deed on Facebook.
People can become filled with pride or get off on being in a position to help the poor beggar too. Nothing Christian about that. Think of the story of Lazurus and the rich man in the bible. The rich man was very judgmental, but thought because he was giving alms, and doing surfacy things that are considered good, he was right with God. However, when he saw pathetic Lazerus thanked God for not being like him. In short, the man was rich in material goods and what the world thinks is good, but his heart was filled with pride and judgement. When he died, he burned in hell, but Lazerus was elevated to heaven for his humbleness. Not begging....or because of his poverty, but because of his HUMILITY.
Forget worrying about if you're doing the Christian thing. It's more complicated than whether you helped this person or not. It's all about what is in everyone's heart, what you're called to do, and whether you're truly equipped to answer that call. Sometimes it isn't our businesss or place to help someone.
Everyone's comments here are valid to a point. But if you're looking for God's approval, then you'll probably have to look somewhere else like the bible.